Shortly after noon, NS said leaks from two of the cars had been addressed. Of the 21 cars that derailed, 19 carried heavy crude, while two carried liquefied petroleum gas. The NS consist included 120 cars overall. Cleanup efforts were ongoing despite severe winter weather blanketing the Northeast.

The train was heading east from Conway, Pa., to Morrisville, Pa., when it derailed near Vandergrift, a town in the western portion of the state. Some of the crude on board reportedly was destined for an asphalt plant in Paulsboro, N.J., owned by San Antonio-based NuStar Energy, L.P.

During the derailment some of the rail cars struck a building which fabricates metal products. There were no injuries. There was no fire or explosion. There is no fire," Norfolk Southern said in a statement.

The incident occurred one day after the Railway Supply Institute Committee on Tank Cars (RSICTC) publicly urged the U.S. Department of Transportation to move proactively in implementing new safety measures for tank cars carrying crude oil and ethanol.